The present invention relates to speed retarding governors and in particular to a speed retarding centrifugal governor for traversing typewriter carriages. Carriage retarding governors as disclosed in the prior art include a plurality of pivotally supported heavy flyweights that are coupled to a traversing carriage and respond to the carriage speed thereto. The flyweights are pivotally supported on a rotatable spring drum that is coupled to the carriage by a cord. As the carriage traverses under the urge of the power supplied by the spring drum disc, the spring drum disc rotates. The flyweights, being attached to the spring drum disc are also urged to rotate and the centrifugal force on the flyweights coupled with the mass causes the flyweights to pivot outward where they frictionally contact the inner peripheral surface of the stationary spring drum housing, thereby retarding the speed of the traversing carriage. To prolong the life of the flyweights, replaceable pads are inserted on the outer periphery of the flyweights. These pads contact the inner surface of the spring drum housing when the flyweights are subjected to the effect of centrifugal force. For example, U.S. Pat. No. 2,829,754 granted to J. H. Norcross on Apr. 8, 1958 discloses a pair of flyweights pivotally supported on a rotatable disc within a spring drum housing. The outermost surface of the flyweights have a nylon pad inserted therein. As the carriage traverses, a gear on the spring drum that powers the carriage traverses, engages a pinion on the governor, which in turn engages a spring clutch that couples the power from the rotating pinion to the shaft on which the flyweights are attached. The flyweights pivot outward about their pivot and the nylon inserts contact the inner peripheral surface of the housing to effect a reduction in the speed of the carriage as the carriage traverses. Therefore, the effectiveness of the governor is entirely dependent on the ability of the fly-weights to freely pivot within the spring drum housing and to contact the internal peripheral surface evenly.
Since the prior art flywights are physically confined to pivot about an axis, the outward movement thereof describes an arc about the pivot and therefore only one restricted portion of the flyweights will contact the housing whereby the prior art braking contact surface is limited. In the event there is any binding about the flyweight pivots and the flyweights cannot freely pivot, the governor becomes ineffective or its effectiveness is severely restricted.
In contrast, the present inventive concept teaches a pair of non-pivotal flyweight segments that are floatably disposed within a housing to provide a more uniform contact between the segments and the housing which results in a more efficient governor. Another example of a governor that utilizes centrifugal flyweights is U.S. Pat. No. 3,645,363 granted to G. Fuths on Feb. 29, l972. U.S. Pat. No. 3,645,363 discloses a pair of flyweights that are pivotally supported on a camming plate within a brake housing to regulate the speed of a shaft and pinion that engages a carriage rack.
The pivots are supported on the camming plate and adjustably disposed within the brake housing. Therefore, adjustment of the camming plate varies the radial distance from the axis of the shaft to the pivot axis. The closer the pivots are to the center of the shaft axis, the greater the force that is exerted by the flyweights against the inner peripheral surface of the brake housing when the carriage is traversing. Consequently, the braking effect on the traversing carriage is increased. The more distant the pivots are from the center of the shaft axis, the less the force that is exerted by the flyweights against the inner peripheral surface of the brake housing when the carriage is traversing. Consequently, the braking effect on the traversing carriage is decreased. The effectiveness of this speed regulating mechanism is also entirely dependent on the ability of the flyweights to freely pivot within the brake housing and to contact the peripheral surface evenly. Any binding about the pivots will prevent proper pivoting of the flyweights and the effectiveness of the speed regulating mechanism will be adversely affected. Furthermore, since the surface contact of the flyweights is only over a limited area, any uneven contact with the inner peripheral surface of the brake housing will result in erratic braking.
The present invention does not depend on the flyweight pivoting about a fixed support axis, for there is no support axis nor any pivotal motion. The flyweights float within the housing and are therefore self centering and self seating. In other words, the inherent freedom of movement of the floating flyweights allows the entire outer peripheral braking surface of the flyweights to contact the inner peripheral surface of the housing evenly. A drive pin that is fixed to a rotatable carriage coupled drive plate; engages one end of one flyweight to rotate that flyweight radially within the housing to abut the end of the second flyweight. Both flyweights begin to spin and the resulting centrifugal force thrusts and wedges the flyweights against the then stationary housing resulting in a speed limiting drag on the carriage during traverse.
The carriage speed retarding governors of the prior art include flyweights that are pivotally supported on a rotatable drive plate. The speed retarding governors of the prior art further include flyweights that must be freely pivotal in order for them to be fully affected by centrifugal forces when they are rotating. The effectiveness and efficiency of governors employing flyweights having fixed pivots depends on the extremely small frictional forces or bearings at the pivot. Use of bearings increases cost, as does machining to insure low friction. The foregoing undesirable structure is overcome by the elimination of any fixed pivot in the present invention. Furthermore, the mass of the flyweights must be great enough to aid in the braking effect of the flyweights. The present invention does not include pivotal flyweights but floating flyweights. In other words, the flyweights are freely positionable within the governor housing and only restricted in their orientation by their proximity to one another. For example, the flyweights, being substantially semi-circular in contour and each occupying an area of the interior of the circular governor housing are not restricted in their movement other than by the peripheral confines of the housing itself and are free to function within the housing without binding. Furthermore, a fixed member of the rotatable drive plate abuts an end of one of the flyweights to render the governor operational. If some restriction occurs within the governor housing to adversely limit the movement of the flyweights, the fixed member on the drive plate would abut that one flyweight and consequently the second flyweight would respond to the movement of the first flyweight and render both flyweights operational. In addition, the flyweight segments being floatable, are self centering by virtue of their contour and self seating by virtue of their freely positionable floatable structure. In other words, the outer peripheral arcuate braking surface of the flyweight segments will contact the inner peripheral arcuate surface of the governor housing evenly.
In governors employing pivotal flyweights where the effectiveness of the governor depends entirely on the unrestricted pivoting of the flyweights, any binding of the flyweights or bearings would cause the governor to malfunction and require extensive and costly repair or replacement. Moreover, the effective operation of the governor is dependent on its rotational velocity that is predicated by the movement of the traversing carriage. For example, the pivotal movement of the flyweights occurs only when the centrifugal forces generated by the rotating governor are sufficient to urge the flyweights outward of the governor's axis. The fly-weights will therefore remain dormant during the first moments of carriage traverse. As the carriage movement increases, the rotational velocity of the governor also increases to generate gradually increasing centrifugal forces which act upon the flyweights, causing pivotal movement thereof to render the governor operational.
The freely positionable floatable structure in cooperation with the abutting rotating drive member of the present invention overcomes the potential problem of binding. Although the effective operation of the governor of the present invention is still dependent on its rotational velocity, the velocity necessary to render the governor operational is less than the velocity required in the prior art governors and therefore more efficient.
The floatable structure of the flyweights also allows for the use of flyweights having less mass than the prior art. This is possible because the entire mass of the flyweights is in functional engagement with the governor housing, whereas only a portion of the prior art flyweights, that portion beyond the pivots, is in functional engagement.